1. Field of the Invention
This invention relates to a device and a method for etching a body comprising material such as silicon or gallium arsenide. In particular, the invention relates to the volatilization and recondensation of a liquid etchant that is then sprayed in the form of an aerosol jet on the body to be etched.
II. Description of Related Art
Two commonly used methods of etching are wet etching and dry etching. In wet etching, those portions of the body not to be etched are covered with a protective layer of material. Etchant is chosen to chemically react with and etch the unprotected portions of the body while not reacting with the protective layer of material. In conventional wet etching, the body is then immersed in the liquid etchant. Conventional wet etching has the advantage of high selectivity because of the chemical etch mechanism involved. However, because of its isotropic etching characteristics, wet etching has limitations for etching fine geometry patterns. In particular, where deep etching occurs adjacent to a protected surface, etching may occur below the protective layer. Wet etching also uses a significant quantity of chemicals in the etching process. Additionally, etched particles floating free in the liquid etchant may redeposit on the body and thus cause contamination.
Spray etching is a type of wet etching. Spray etching merely sprays very large particles of liquid etchant on the body to be etched. Spray etching displays several of the characteristics of wet etching including the isotropic nature of the etch and the wet etch limitations for etching fine geometry patterns. In spray etching, the quantity of liquid etchant used and the likelihood of contamination through redeposition are reduced as compared to conventional wet etching. Further, in wet etching the body to be etched must be rinsed of etchant promptly after etching. Neither spray etching nor conventional wet etching can etch deep, narrow channels because surface tension prevents etchant from entering and etching such channels.
Dry etching, sometimes called plasma-assisted etching, has the advantage of high etch anisotropy and thus dry etching methods are particularly suitable for fine geometry patterns. However, the selectivity of dry etching is not sufficient to prevent etching of layers or substrates under an etched film. Also, surface radiation damage from dry etching causes problems in device fabrication.